1. Field of the Invention
The present invention relates to filters for fluid supplies of vehicle occupant restraint systems employing combustible gas generators.
2. Description of the Prior Art
Multilayer filter assemblies for vehicle occupant restraint systems employing combustible gas generators are known in the prior art. Exemplary of this art are filters shown in a prior application Ser. No. 539,220, filed Jan. 8, 1975, now U.S. Pat. No. 4,017,100, of Applicant and R. G. Gehrig assigned to the assignee o the present invention and prior application Ser. No. 591,911 of Applicant, filed June 30, 1975, now U.S. Pat. No. 4,012,211, and assigned to the assignee of the present invention.
Certain disadvantages have been noted, however, in the use of such filter assemblies.
One of these is the tendency of solid contaminants to concentrate in certain areas of the filter and thereafter to burn through the filter layers. This tendency is commonly referred to as "pinholing."
Another disadvantage is the tendency of such filters to permit "channelling", that is, bypassing of one or more filter layers by a portion of the flowing gas due to inadequate support of one or more of the layers when intermediate support members are not used or are ineffective.
Still another disadvantage lies in the fact that the prior art filters tend to have high heat capacity, necessitating the use of large amounts of combustible material to effect inflation of the confinement.